Water and materials recovery from fertilizer industry acidic effluents by membrane processes

Recent developments in membrane technology are promising as regards drastic reduction of effluents from process plants, through cleaning and recycling polluted streams until recently considered untreatable. This paper outline s specific R & D activities in this direction. Results are reported, of a s tudy in progress, towards recycling various effluent streams from a fertili zer industrial complex with the use of RO membrane technology. The scope of this study is to determine the technical and economic feasibility of a dua l process target: a) Concentrating selected effluent streams containing val uable compounds and reusing them in fertilizer production processes; at pre sent the cost of treatment (before release) of these environmentally offens ive streams is high. b) Obtaining high quality membrane permeate water to b e used in steam production, and for improving cooling-water quality, thus m inimizing fresh water consumption. Two specific examples are discussed: one of a stream rich in nitrate and ammonium ions and another of a highly acid ic effluent, rich in fluorosilicic and fluoride ions. Results from bench an d short-term pilot scale tests are encouraging with regard to the technical feasibility of membrane processes for achieving the targets set. These tes t results are further used to determine membrane rejection characteristics, to guide the selection of appropriate membranes, and to determine the proc ess concentrate and permeate quality (as a function. of recovery) as well a s the necessary pretreatment. Preliminary economic evaluations are also sum marized which take into account the benefits from materials and water reuse , and from the significantly reduced loads of the ion-exchange facility (fo r water demineralization) and of the final wastewater treatment plant. Thes e results suggest that the application of membrane technology is promising for more efficient and environmentally friendlier plant operation.